CBSE Class 9 Biology Natural Resources Worksheet Set 01

Question. Give brief sketch on advantages and disadvantages on manure and fertilizers.
Answer: Advantages of manure :
(i) It increases the number of friendly microbes.
(ii) It improves the texture of soil by adding organic matter (humus).
(iii) It increases soil fertility, water holding capacity and aeration.
(iv) It reduces soil erosion.
(v) It is cheap.
Disadvantages of manure :
(i) They have fewer amounts of nutrients as compared to fertilizers.
(ii) Manures are bulky and not easy to store and transport.
Fertilizers : These are commercially manufactured inorganic salts containing one or more essential plant nutrients like NPK, which are used to increase soil fertility.
Advantages of fertilizers :
(i) They are nutrient specific and required in small amounts.
(ii) They are water soluble and absorbed by the plant easily.
(iii) They are easy to store and transport. Disadvantages of fertilizers :
(i) Fertilizers can change the soil structure by killing the soil microbes.
(ii) Fertilizers can change the chemical composition of soil.
(iii) Accumulation of fertilizers in water bodies causes eutrophication.

Question. What are the main characters required in a crop during its improvement practices?
Answer:
The useful characters that are required in a crop during its improvement :
(i) Disease resistance
(ii) Response to fertilizer
(iii) Product quality
(iv) High yield
(iii) Intergeneric – between two different genera

Question. What are the main characters required in a crop during its improvement practices?
Answer: The useful characters that are required in a crop during its improvement :
(i) Disease resistance
(ii) Response to fertilizer
(iii) Product quality
(iv) High yield

Question. Give difference between apiculture and aquaculture.
Answer: Domestication of honeybees or production of honey and wax on commercial bases is called apiculture. Farming and management of fish and other aquatic animals and plants in water is called aquaculture.

Question. What are fertilizers? Excess use of fertilizers is not advisable, explain.
Answer: Fertilizers are commercially produced plant nutrients. They supply nitrogen, phosphorus and potassium. hey are used to ensure good vegetative growth, giving rise to healthy plants.
Excessive use of fertilizers are not advisable as:
(a) It leads to soil and water pollution.
(b) It can destroy the fertility of soil.

Question. Why there is necessity of animal husbandry?
Answer: To fulfil growing demand for milk, eggs and meat and providing self employment livestock production is needed.

Question. What factors may be responsible for losses of grains during storage? Also mention any two preventive measures to control loss of grains during storage.
Answer: Factors responsible for losses are :
Biotic : Insects, rodents, fungi, mites and bacteria.
Abiotic : Inappropriate moisture and temperatures in the place of storage. Cleaning of the produce before storage, proper drying of the produce first in sunlight and then in shade, and fumigation are preventive measures to control loss of grains during storage.

Question. What are the various methods of irrigation in India?
Answer: Most of agriculture in India is rain-fed, several different kinds of irrigation system are adopted to supply water to agricultural lands. The resources are-wells, canals,rivers and tanks.
(i) Wells : Dug wells and tube wells. In dug wells water is collected from water— bearing strata.
(ii) Tubewells : Water from deeper strata.
(iii) Canals : Most extensive irrigation system. Canals receive water from reservoirs or rivers. The main canal is divided into branch canals having further distributaries to irrigate fields.
(iv) River lift system : Water is directly drawn from the river for supplementing irrigation in areas close to rivers.
(v) Tanks : These are small storage reservoirs, which intercept and store the run-off of smaller catchment areas.

Question. What are the factors for which variety improvement of crop is done?
Answer: (a) Higher yield : It increases production of crop.
(b) Biotic and abiotic resistance : Crop should be resistant to biotic factors like diseases, insects, pests and abiotic factors like drought, salinity, heat, etc.
(c) Change in maturity duration : Short-duration maturity allows farmer to grow more crops in a year with short duration maturity and reduces the crop production cost.
(d) Wider adaptability : Crop should be able to adapt to changing environmental conditions.
(e) Desirable agronomic characteristics : Crop should have tallness and dwarfness as per need. Dwarfness is required for cereals, so that few nutrients are consumed.

Question. Write a paragraph in your own words on each of the following.
(a) Preparation of soil,
(b) Sowing,
(c) Weeding,
(d) Threshing
Answer: 
(a) Preparation of soil : Preparation of soil is the first step of farming. Soil is loosened and turned over. This helps in making the soil more airy so that roots can breathe in air. Moreover, loosening of soil also facilitates better penetration of roots into the soil. Seeds can be easily sown in loosened soil.
(b) Sowing : The method of putting the seeds into soil is called sowing. Traditionally, seed is sown manually by spreading the seeds by hands. This process is called broadcasting. Seed drills are used when sowing needs to be done on a large scale.
(c) Weeding : Removal of weeds is called weeding. Unwanted plants which grow along with the crop are called weeds. They compete for resources; like sunlight, water and air; with the main crop. So, it is necessary to remove weeds for proper growth ofcrops. Weeding is usually done manually by using  hands and sickles. Sometimes weedicides are also sprayed.
(d) Threshing : Separation of grains from harvested stems is called threshing. For smaller quantity, threshing is done by hands. For somewhat bigger quantity, threshing is done using animal; especially bullocks. Animals are made to trample over the harvested stock which helps in separation of grains. Threshing machines are used for bigger  quantities.

Question. What is the advantage of composite fish culture?
Answer: The composition of six species of fish in composite fish is highly advantageous because:
(i) These fishes do not compete for food among themselves
(ii) They have different food habit
(iii) Food in all parts of pond is utilized due to different food habits

Question. Why Apis mellifera is adopted for domestication to produce honey?
Answer: The Italian species of honey bee, i.e. Apis mellifera is adopted for its many good qualities. They :
(i) sting less
(ii) have good honey collection capacity
(iii) produce with less swarming
(iv) have ability to protect itself from enemy
(v) stay in beehives for a long time

Question. “Shorter the duration of the crop from sowing to harvesting, the more economical is the variety.” Give reason for this.
Answer: Farmers can grow more crops in a year due to short duration of crop growth, and reduce the cost of crop production.

Question. Name different types of crop production practices involved in India.
Answer: They are (a) no cost production, (b) low cost production and (c) high cost production.

Question. Name the nutrients that plant obtains from air and water.
Answer: Air - Carbon and oxygen
        Water - Hydrogen and oxygen

Question. Name the products obtained from apiculture.
Answer: Honey and wax both are obtained from apiculture.

Question. What is meant by bee-keeping?
Answer: Rearing of bees for the production of honey on a large scale is called bee-rearing.

Question. Name two exotic breeds of cattle.
Answer: Jersey and Brown Swiss

Question. What are the practices used for dairy industry?
Answer: The practices used for dairy industry to get the optimum yield are :
(i) Shelter : The shelter should be clean, spacious and airy.
(ii) Feeding : Proper food at proper time is essential for dairy animals.
(iii) Rearing of animals : Providing them proper health care and protection from pathogens, diseases and proper vaccination.
(iv) Breeding : The crossing of different variety of milch animals to obtain a breed that can produce more yield of milk.

Question. Large amount of food grains get spoiled every year in India due to improper storage of food grains. How can this be avoided?
Answer: Food grains get spoiled by insects, fungi, rodents, bacteria, moisture at the place of storage. Storage losses can be reduced by taking some preventive and control measures.
(i) The seeds that are to be stored should be dry
(ii) The grains should be cleaned
(iii) The grains should be fumigated using chemicals that kills pest.
(iv) The storage houses should be waterproof.
(v) The grains should be stored in sealed gunny bags.
(vi) The bags should be kept few centimetres away from the wall.
(vii) The walls and the floor should be water-proof with no holes in it, to avoid rodents, pests.

Question. What are weeds? How can we control them? Give different methods of weed control.
Answer: Unwanted plants which grow along with crops are called weeds. Weeds compete with crops for natural resources; like sunlight, water and nutrients. Thus, weeds hamper the growth of crops. Weeds are usually removed manually by hands and by sickles. This process is called weeding. Sometimes, weedicides are also sprayed to kills weeds. Weeds can be controlled by different methods :
(a) Weedicides : These are the chemicals sprayed on the weeds to kill them. Excessive use is poisonous and causes environmental pollution.
(b) Mechanical removal : In this method weeds are uprooted by removing manually or by machines.
(c) Preventive methods : Proper seed bed preparation, timely sowing of crops, intercropping and crop rotation helps in weed control.

Question. Explain different types of fisheries.
Answer: The different types of fisheries are marine fisheries; inland fisheries, capture fishing, mariculture and aquaculture.
(i) Marine fisheries : Marine fishes are caught using fishing nets.
(ii) Mariculture : Marine .fishes are cultured in seawater.
(iii) Inland fisheries : The fisheries done in freshwater resources like canals, ponds, reservoirs and rivers.
(iv) Capture fishing : It is done in sea-water, estuaries and lagoons.
(v) Aquaculture : Culture of fish done in different water bodies is called aquaculture.

Question. Explain how soil gets affected by the continuous plantation of crops in a field.
Answer: Continuous plantation of crops in a field affects soil fertility. Plants utilize all the nutrients from soil which leads to depletion of nutrients in the soil. As a result, soil fertility reduces drastically.

Question. A group of gardening club students prepared a  kitchen garden in the school campus and did organic farming to grow the vegetables. Then the students presented their group work in the assembly to spread the awareness and make students understand the importance of organic products.
(a) What is horticulture?
(b) What is green manure?
Answer: (a) Hotriculture is the commercial production of vegetables and fruits.
(b) The green plants like sun hemp are turned into the soil which enriches the soil with nitrogen and phosphorus and is called green manure.

Question. What are the three advantages of shorter duration of the crop in between sowing and harvesting?
Answer: Short durations allow farmers to grow multiple rounds of crops in a year. Short duration also reduces the cost of crop production. Uniform maturity makes the harvesting process easy and reduces losses during harvesting.

Question. Which nutrients are supplied by cereals and pulses?
Answer: Carbohydrate is supplied by cereals and protein is supplied by pulses.

Question. Define animal husbandry.
Answer: Animal husbandry is the management and care of farm animals by humans for profit.

Question. Name two factors responsible for wastage of grains during storage.
Answer: Factors responsible for such losses are :
Biotic : insects, rodents, fungi, mites and bacteria,
Abiotic : inappropriate moisture and temperatures in the place of storage.

Question. (i) Name an exotic variety of honey bee grown in India.
(ii) What is called the rearing of fish on a large scale?
Answer:
(i) Apis cerana indica
(ii) Pisciculture

Question. Is breeding and rearing of Bombay duck part of poultry farming or a part of pisciculture?
Answer: It is a part of pisciculture as Bombay duck is fish not a duck.

Question. What is the tremendous increase in the production of eggs in India known as?
Answer: Golden revolution and Silver revolution.

Question. State the preventive and control measures used before grains are stored.
Answer:
(i) Cleaning of the grains.
(ii) Keep seeds in sunlight to provide moisture.
(iii) Using chemicals that kills pest.

Question. Environment is controlled by
(A) matter
(B) energy
(C) both
(D) only (2) is correct

Answer: C

Question 1. What is the green house effect ?
Answer: The greenhouse effect is a natural phenomenon by which certain gases (known as greenhouse gases like carbon dioxide, methane, and water vapor) in the Earth's atmosphere trap heat radiated from the Earth's surface, preventing it from escaping into outer space and keeping the planet warm enough to sustain life.
In simple words: It is the trapping of heat by atmospheric gases to keep the Earth warm, much like a glass greenhouse traps heat for plants.

Exam Tip: Mention both the trapping of thermal radiation and the specific gases involved to secure full marks.

Question 2. How is ozone layer formed ?
Answer: The ozone layer is formed in the stratosphere through the interaction of ultraviolet (UV) radiations with oxygen molecules. High-energy UV radiation splits molecular oxygen (\(\text{O}_2\)) into free oxygen atoms (\(\text{O}\)). These highly reactive oxygen atoms then combine with unbroken oxygen molecules (\(\text{O}_2\)) to form ozone (\(\text{O}_3\)) according to the reaction: \(\text{O}_2 + \text{O} \rightarrow \text{O}_3\).
In simple words: Sunlight splits oxygen molecules, and the resulting single oxygen atoms join with other oxygen molecules to form ozone.

Exam Tip: Always write the chemical steps (\(\text{O}_2 \rightarrow \text{O} + \text{O}\) followed by \(\text{O} + \text{O}_2 \rightarrow \text{O}_3\)) when explaining ozone formation.

Question 3. What is biogeochemical cycles ?
Answer: Biogeochemical cycles refer to the constant flow and recycling of nutrients and elements (such as carbon, nitrogen, oxygen, and water) between the biotic (living organisms) and abiotic (non-living components like air, water, and soil) components of the biosphere.
In simple words: It is the cyclic movement of essential elements between living things and their physical environment.

Exam Tip: Break down the term 'bio' (living), 'geo' (rocks/earth), and 'chemical' (elements) in your mind to remember the definition accurately.

Question 4. What is water cycle ?
Answer: The water cycle (or hydrological cycle) is the continuous movement of water on, above, and below the surface of the Earth. It involves the processes of evaporation of water from water bodies and transpiration from plants, condensation of water vapor to form clouds, precipitation in the form of rain or snow, and collection/runoff back into oceans and rivers.
In simple words: It is the continuous circulation of water from the Earth's surface to the atmosphere and back down as rain.

Exam Tip: Use a flowchart sequence (Evaporation -> Condensation -> Precipitation -> Collection) in your answer for maximum clarity.

Question 5. Give two ways in which \(\text{CO}_2\) is fixed.
Answer: The two primary ways in which carbon dioxide (\(\text{CO}_2\)) is fixed in nature are:
1. Photosynthesis: Green plants absorb \(\text{CO}_2\) from the atmosphere and convert it into glucose in the presence of sunlight and chlorophyll.
2. Marine Fixation: Many marine organisms use carbonate dissolved in sea water to make their shells (such as calcium carbonate).
In simple words: Plants fix carbon dioxide through photosynthesis, and sea animals use dissolved carbonates to build shells.

Exam Tip: Clearly state photosynthesis as the primary terrestrial mechanism.

Question 6. Name the major green house gas responsible for causing global warming.
Answer: Carbon dioxide (\(\text{CO}_2\)) is the major greenhouse gas responsible for causing global warming, primarily due to its high abundance and significant contribution to enhanced heat trapping.
In simple words: Carbon dioxide is the main gas that traps extra heat and causes global warming.

Exam Tip: Though water vapor is a powerful greenhouse gas, carbon dioxide is universally recognized as the primary driver of anthropogenic global warming.

Question 7. What is the role of nitrogen fixing bacteria in the biosphere ?
Answer: Nitrogen-fixing bacteria (such as Rhizobium found in the root nodules of leguminous plants, as well as free-living bacteria like Azotobacter) convert inert atmospheric nitrogen gas (\(\text{N}_2\)) into usable nitrogenous compounds like nitrates and ammonia, which can be easily absorbed and utilized by plants for protein synthesis.
In simple words: They convert unuseable nitrogen gas from the air into usable plant nutrients.

Exam Tip: Mention specific examples like Rhizobium and leguminous plants to score full marks.

Question 8. How do ozone layer gets depleted ?
Answer: The ozone layer is depleted by the release of synthetic chemical compounds, most notably chlorofluorocarbons (CFCs), into the atmosphere. When CFCs reach the stratosphere, ultraviolet radiation breaks them down to release reactive chlorine atoms. These chlorine atoms act as catalysts to repeatedly break down ozone (\(\text{O}_3\)) molecules into oxygen molecules (\(\text{O}_2\)), destroying the ozone layer faster than it can naturally form.
In simple words: Chemicals like CFCs release chlorine in the upper atmosphere, which destroys ozone molecules.

Exam Tip: Emphasize the catalytic role of chlorine atoms in breaking multiple ozone molecules.

Question 9. How does ozone layer protect us from harmful effects of the environment ?
Answer: The ozone layer absorbs high-energy, harmful ultraviolet (UV) radiations (specifically UV-B and UV-C rays) coming from the sun, preventing them from reaching the Earth's surface. This protects living organisms from severe damage such as skin cancer, damage to eyes (cataracts), suppression of the immune system, and destruction of crops and marine phytoplankton.
In simple words: It acts as a protective shield that blocks harmful ultraviolet rays from the sun.

Exam Tip: Mention specific health hazards like skin cancer and cataracts to demonstrate a thorough understanding.

Question 10. How do water cycle help the organisms ?
Answer: The water cycle helps organisms by:
1. Ensuring a continuous supply of fresh water to terrestrial organisms for drinking and metabolic processes.
2. Facilitating the transport of minerals and nutrients within the body of organisms and across ecosystems.
3. Regulating climate and temperature conditions suitable for survival.
In simple words: It replenishes fresh water supplies necessary for the survival and daily activities of all living things.

Exam Tip: Focus on both hydration and nutrient transport aspects.

Question 11. How is oxygen maintained in the atmosphere ?
Answer: Oxygen is maintained in the atmosphere through a delicate balance governed by the oxygen cycle. Oxygen is consumed during respiration by animals, humans, and microbes, as well as during combustion and decomposition. It is replenished in the atmosphere exclusively by green plants through the process of photosynthesis, where they release oxygen as a byproduct.
In simple words: Plants release oxygen during photosynthesis to balance the oxygen used up by breathing and burning.

Exam Tip: Contrast consumption processes (respiration, combustion) with production (photosynthesis).

Question 12. What are CFC's and why are there considered as harmful for the life on earth ?
Answer: CFCs stand for chlorofluorocarbons, which are synthetic chemical compounds containing carbon, chlorine, and fluorine, historically used in refrigerators, air conditioners, and aerosol sprays. They are considered harmful because they are extremely stable in the lower atmosphere, rise up into the stratosphere intact, and release chlorine atoms upon exposure to UV light, which systematically destroys the protective ozone layer.
In simple words: CFCs are man-made chemicals that rise to the upper atmosphere and destroy the ozone layer.

Exam Tip: Define the abbreviation CFC clearly and link it directly to ozone destruction.

Question 13. What is global warming ? What is its effects?
Answer: Global warming is the gradual increase in the overall temperature of the Earth's atmosphere caused by the enhanced greenhouse effect due to increased levels of greenhouse gases like carbon dioxide and methane.
Effects of global warming include:
1. Melting of polar ice caps and glaciers, leading to a rise in sea levels and coastal flooding.
2. Disruption of weather patterns, causing extreme weather events like droughts, floods, and severe storms.
3. Loss of biodiversity and destruction of fragile habitats such as coral reefs.
In simple words: It is the heating up of the Earth causing melting ice, rising seas, and extreme weather.

Exam Tip: Divide your answer neatly into definition and bulleted effects.

Question 14. With the help of labelled diagram explain in brief the carbon cycle in nature ?
Answer: The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, geosphere, hydrosphere, and atmosphere of the Earth. Carbon dioxide in the atmosphere is taken up by plants for photosynthesis. Animals eat plants, incorporating organic carbon into their bodies. Both plants and animals return carbon dioxide to the atmosphere through respiration. Upon death, decomposers break down organic matter, releasing carbon into the soil and air. Additionally, combustion of fossil fuels and volcanic activity release large amounts of \(\text{CO}_2\) back into the atmosphere.
In simple words: Carbon moves between air, plants, animals, and soil through breathing, eating, decomposition, and burning.

Exam Tip: Include a clear block diagram showing the interchange between atmospheric carbon dioxide, plants, animals, and fossil fuels.

Question 15. State two forms in which elemental oxygen is found in the earths atmosphere. Mention in brief the essential function performed by each at the place they found.
Answer: The two forms in which elemental oxygen is found in the Earth's atmosphere are:
1. Diatomic Oxygen (\(\text{O}_2\)): Found in the lower atmosphere (troposphere). Its essential function is to support aerobic respiration in living organisms (humans, animals, plants) and facilitate combustion.
2. Triatomic Oxygen or Ozone (\(\text{O}_3\)): Found in the stratosphere. Its essential function is to act as a shield by absorbing harmful ultraviolet (UV) rays from the sun, protecting life on Earth from radiation damage.
In simple words: Oxygen (\(\text{O}_2\)) helps us breathe, while ozone (\(\text{O}_3\)) protects us from UV rays in the upper atmosphere.

Exam Tip: Clearly differentiate between tropospheric diatomic oxygen and stratospheric ozone.

Question 16. Illustrate nitrogen cycle in biosphere.
Answer: The nitrogen cycle is a biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The main stages of the nitrogen cycle are:
1. Nitrogen Fixation: Atmospheric nitrogen (\(\text{N}_2\)) is converted into ammonia or nitrates by nitrogen-fixing bacteria (like Rhizobium) or via lightning.
2. Assimilation: Plants absorb these nitrates from the soil and incorporate them into plant proteins, which are then consumed by animals.
3. Ammonification: Decomposers convert nitrogenous waste and dead organic matter back into ammonia.
4. Nitrification: Ammonia is converted into nitrites and then nitrates by nitrifying bacteria (such as Nitrosomonas and Nitrobacter).
5. Denitrification: Denitrifying bacteria convert soil nitrates back into atmospheric nitrogen gas, completing the cycle.
In simple words: Nitrogen is fixed by bacteria, used by plants and animals, returned to soil by decay, and released back into the air by bacteria.

Exam Tip: Mention all five key processes (Fixation, Assimilation, Ammonification, Nitrification, Denitrification) to achieve full credit.